JP6428327B2 - Power module substrate with heat sink, power module, and method for manufacturing power module substrate with heat sink - Google Patents

Description

  The present invention includes an insulating layer, a circuit layer formed on one surface of the insulating layer, a metal layer formed on the other surface of the insulating layer, and an opposite side of the metal layer to the insulating layer. The present invention relates to a power module substrate with a heat sink, a power module including the power module substrate with a heat sink, and a method for manufacturing the power module substrate with a heat sink.

In general, in a power semiconductor element for high power control used for controlling wind power generation, electric vehicles, hybrid vehicles, etc., since the amount of heat generated is large, as a substrate on which such a power semiconductor element is mounted, for example, A ceramic substrate made of AlN (aluminum nitride), Al ₂ O ₃ (alumina), a circuit layer formed on one surface of the ceramic substrate, and a metal layer formed on the other surface of the ceramic substrate, The power module substrate provided has been widely used.
In addition, in order to efficiently dissipate heat generated from a mounted semiconductor element or the like, there is provided a power module substrate with a heat sink in which a heat sink is bonded to the metal layer side.

  For example, in Patent Document 1, a circuit layer and a metal layer of a power module substrate are made of aluminum or an aluminum alloy, and a heat sink is made of aluminum or an aluminum alloy, and the metal layer and the heat sink are soldered or brazed. The board | substrate for power modules with a heat sink joined by this is disclosed.

  Further, in Patent Document 2, a circuit layer and a metal layer made of aluminum are formed on one surface and the other surface of a ceramic substrate, and a copper plate is disposed between the metal layer and the heat sink. The metal layer, the copper plate, and the copper plate And a heat module substrate with a heat sink in which the heat sink and the heat sink are respectively soldered.

  Further, Patent Document 3 discloses a power module substrate with a heat sink in which a circuit layer and a metal layer of a power module substrate are made of aluminum or an aluminum alloy and a heat sink is made of aluminum or an aluminum alloy. In other words, a bonding material composed of copper or a copper alloy is interposed between the metal layer and the bonding material, and the bonding material and the heat sink are solid phase diffusion bonded.

JP 2008-016813 A JP 2007-250638 A JP 2014-060215 A

  By the way, recently, higher output of power semiconductor elements and the like has been promoted, and a severe heat cycle has been applied to the power module substrate with a heat sink on which the power semiconductor element is mounted. There is a demand for a power module substrate with a heat sink having excellent bonding reliability with respect to the cycle.

  Here, in the power module substrate with a heat sink described in Patent Document 1, when the metal layer and the heat sink are soldered, a crack is generated in the solder at the time of heat cycle load, and the bonding rate is reduced. There was a problem that the thermal resistance increased. In addition, when the metal layer and the heat sink are brazed, there is a possibility that the ceramic substrate is cracked during a heat cycle load.

  In the power module substrate with heat sink described in Patent Document 2, since the metal layer and the copper plate, and the copper plate and the heat sink are respectively soldered, the solder is cracked at the time of heat cycle load, and the bonding rate is lowered. As a result, there is a problem that the thermal resistance increases.

In the power module substrate with a heat sink shown in Patent Document 3, a bonding material composed of copper or a copper alloy is interposed between the metal layer and the heat sink, and the metal layer, the bonding material, the bonding material, and the heat sink are respectively inserted. Solid phase diffusion bonding is performed, and a bonding material made of copper or a copper alloy remains at the bonding interface between the metal layer and the heat sink.
In the bonding interface between the metal layer and the heat sink, in the region of the metal layer and the heat sink side has a high existence ratio of Al atom, as shown in the state diagram of FIG. 1, the aluminum content is large θ phase (CuAl ₂ ) And the like are formed. On the other hand, in the vicinity region of the bonding material made of copper or copper alloy, the γ ₂ phase (Cu ₉ Al ₂ ), δ phase (Cu ₃ Al ₂ ), ζ ₂ having a high Cu atom content and a high copper content. Intermetallic compound phases such as the phase (Cu ₅₅ Al ₄₅ ) and the η ₂ phase (CuAl) are formed. The θ phase described above is a relatively fragile phase, and the η ₂ phase (CuAl) and the ζ ₂ phase (Cu ₅₅ Al ₄₅ ) are phases with high hardness.

Since the intermetallic compound phase described above is formed in accordance with the abundance ratio of Al and Cu, the η ₂ phase (Cu ₂ ) is adjacent to the θ phase (CuAl ₂ ) formed in the metal layer and the heat sink side region. CuAl) or ζ ₂ phase (Cu ₅₅ Al ₄₅ ) is formed. When a thick η ₂ phase (CuAl) or ζ ₂ phase (Cu ₅₅ Al ₄₅ ) is formed so as to be adjacent to the fragile θ phase, the fragile θ phase is applied when a heat cycle is applied. Cracks easily.
For this reason, in the power module substrate with a heat sink shown in Patent Document 3, when a severe heat cycle is applied, a crack may occur in the intermetallic compound phase and the bonding rate may decrease, and the thermal resistance may increase. there were.

  The present invention has been made in view of the above-described circumstances, and includes a power module substrate with a heat sink that can suppress the occurrence of cracks and the like at the joint interface even when a severe heat cycle is applied, and the heat sink. It aims at providing the manufacturing method of the power module provided with the board | substrate for power modules, and the board | substrate for power modules with a heat sink.

In order to solve such problems and achieve the above object, a power module substrate with a heat sink according to the present invention includes an insulating layer, a circuit layer formed on one surface of the insulating layer, and the insulating layer. A power module substrate with a heat sink, comprising: a metal layer formed on the other surface of the metal layer; and a heat sink disposed on a surface of the metal layer opposite to the insulating layer. The bonding surface with the heat sink and the bonding surface with the metal layer of the heat sink are made of aluminum or an aluminum alloy, and the metal layer and the heat sink are connected via a bonding material made of copper or a copper alloy. A diffusion bonding layer having an intermetallic compound of Al and Cu is formed at the bonding interface between the metal layer and the heat sink. In diffusion bonding layer, the thickness of the high concentration layer of Cu Cu concentration of more than 50 mol% are as 30μm or less, that the thickness of the diffusion bonding layer is in a range of 3μm or 110μm or less It is a feature.

  In the power module substrate with a heat sink having this configuration, the metal layer and the heat sink are bonded by solid phase diffusion bonding via a bonding material made of copper or a copper alloy, and the metal layer and the heat sink A diffusion bonding layer having an intermetallic compound of Al and Cu is formed between them. In this diffusion bonding layer, the thickness of the high concentration Cu layer at which the Cu concentration is 50 mol% or more is 30 μm or less. Therefore, at the bonding interface between the metal layer and the heat sink, the region where the ratio of Cu atoms is high is thin, and the hard intermetallic compound is adjacent to the relatively brittle θ phase formed on the metal layer and the heat sink side. Even when the phase is not formed thick and a severe heat cycle is applied, the formation of cracks in the intermetallic compound phase can be suppressed. Thereby, it becomes possible to improve the joining reliability with respect to a heat cycle.

In addition, since the thickness of the diffusion bonding layer having an intermetallic compound of Al and Cu formed between the metal layer and the heat sink is in the range of 3 μm to 110 μm, the metal layer and the heat sink Are securely bonded, and the bonding strength can be ensured. Further, since the diffusion bonding layer is not formed to be thicker than necessary, it is possible to suppress the occurrence of cracks in the diffusion bonding layer even when a severe heat cycle is applied.

A power module according to the present invention includes the above power module substrate with a heat sink and a semiconductor element bonded to a surface of the circuit layer opposite to the insulating layer.
According to the power module with a heat sink of the present invention, since the power module substrate with a heat sink described above is provided, the bonding rate between the power module substrate and the heat sink decreases even when a severe heat cycle is applied. To suppress the increase in thermal resistance. For this reason, it is possible to efficiently dissipate heat generated from the semiconductor element toward the heat sink.

The method for manufacturing a power module substrate with a heat sink according to the present invention includes an insulating layer, a circuit layer formed on one surface of the insulating layer, a metal layer formed on the other surface of the insulating layer, and the metal A heat module with a heat sink, comprising: a heat sink disposed on a surface of the metal layer opposite to the insulating layer, wherein the metal layer has a bonding surface with the heat sink, and the heat sink. The bonding surface with the metal layer is made of aluminum or an aluminum alloy, and includes a heat sink bonding step for bonding the metal layer and the heat sink. In the heat sink bonding step, the metal layer and the metal layer Solid-phase diffusion bonding is performed between the heat sink and a bonding material made of copper or a copper alloy, and the thickness of the bonding material is 1 μm or more and 50 μm. In the heat sink bonding step, the metal layer and the heat sink are stacked via the bonding material, and a load of 0.29 MPa to 3.5 MPa is applied in the stacking direction. Thus, the metal layer and the heat sink are solid-phase diffusion bonded by holding at a holding temperature of 400 ° C. or more and less than 548 ° C. for 0.1 hour or more and 4 hours or less .

According to the method for manufacturing a power module substrate with a heat sink having this configuration, in the heat sink joining step of joining the metal layer and the heat sink, a joining material made of copper or a copper alloy between the metal layer and the heat sink. Since the thickness of the bonding material is less than 50 μm, the Cu atoms in the bonding material are bonded to the bonding surface of the metal layer and the heat sink when solid-phase diffusion bonding is performed. By sufficiently diffusing to the bonding surface side, a region having a high Cu atom content at the bonding interface between the metal layer and the heat sink becomes thin, and a η ₂ phase (CuAl) or a ζ ₂ phase (Cu ₅₅ Al ₄₅ ) or the like, and the formation of a thick high-concentration Cu layer with a Cu concentration of 50 mol% or more can be suppressed.
On the other hand, since the thickness of the bonding material made of copper or copper alloy is 1 μm or more, it is possible to secure Al atoms on the bonding surface of the metal layer and Cu atoms that are solid-phase diffused with Al atoms on the bonding surface of the heat sink. In addition, the metal layer and the heat sink can be reliably solid-phase diffusion bonded.

In addition, the solid phase diffusion bonding conditions were adopted in which a load of 0.29 MPa or more and 3.5 MPa or less was applied in the stacking direction and the temperature was maintained at a holding temperature of 400 ° C. or more and less than 548 ° C. for 0.1 hour or more and 4 hours or less. Therefore, the metal layer and the heat sink can be reliably bonded, and the Cu atoms of the bonding material are sufficiently diffused, so that the η ₂ phase (CuAl) or ζ ₂ phase (Cu ₅₅ Al ₄₅ ) It is possible to reliably suppress the formation of a thick high-concentration Cu layer having a Cu concentration of 50 mol% or more.

  According to the present invention, a power module substrate with a heat sink that can suppress the occurrence of cracks or the like in an intermetallic compound phase or a diffusion bonding layer even when a severe heat cycle is loaded, and the power module substrate with a heat sink It becomes possible to provide the manufacturing method of the power module provided and the board | substrate for power modules with a heat sink.

It is a binary phase diagram of Cu and Al. It is a schematic explanatory drawing of the board | substrate for power modules with a heat sink and power module which are embodiment of this invention. It is a schematic diagram of the joining interface of the metal layer and heat sink of the board | substrate for power modules with a heat sink shown in FIG. It is a flowchart which shows the manufacturing method of the board | substrate for power modules with a heat sink which is embodiment of this invention. It is explanatory drawing which shows the manufacturing method of the board | substrate for power modules with a heat sink which is embodiment of this invention. It is a schematic explanatory drawing of the board | substrate for power modules with a heat sink and power module which are other embodiment of this invention. It is a schematic explanatory drawing of the board | substrate for power modules with a heat sink and power module which are other embodiment of this invention.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
In FIG. 2, the board | substrate 30 for power modules with a heat sink and the power module 1 which are one Embodiment of this invention are shown.

The power module 1 includes a power module substrate 30 with a heat sink, and a semiconductor element 3 bonded to one surface (the upper surface in FIG. 2) of the power module substrate 30 with a heat sink via a solder layer 2. ing.
Here, the solder layer 2 is made of, for example, a Sn—Ag, Sn—In, or Sn—Ag—Cu solder material.

The power module substrate with heat sink 30 according to the present embodiment includes a power module substrate 10 and a heat sink 31 bonded to the power module substrate 10.
The heat sink 31 is used to dissipate heat on the power module substrate 10 side, and as shown in FIG. 2, is a heat sink made of aluminum or an aluminum alloy. In the present embodiment, the heat sink 31 is formed of a rolled sheet of A6063, and the thickness thereof is set within a range of 1 mm or more and 6 mm or less.

The power module substrate 10 has a ceramic substrate 11, a circuit layer 12 disposed on one surface (the upper surface in FIG. 2) of the ceramic substrate 11, and the other surface (lower surface in FIG. 2) of the ceramic substrate 11. And a disposed metal layer 13.
The ceramic substrate 11 prevents electrical connection between the circuit layer 12 and the metal layer 13, and is composed of AlN (aluminum nitride) having high insulation in this embodiment. Here, the thickness of the ceramic substrate 11 is set within a range of 0.2 mm or more and 1.5 mm or less, and is set to 0.635 mm in the present embodiment.

  As shown in FIG. 5, the circuit layer 12 is formed by joining an aluminum plate 22 made of aluminum or an aluminum alloy to one surface of the ceramic substrate 11. In the present embodiment, a 2N aluminum rolled plate having a purity of 99 mass% or more is used as the aluminum plate 22 constituting the circuit layer 12. A circuit pattern is formed on the circuit layer 12, and one surface (the upper surface in FIG. 2) is a mounting surface on which the semiconductor element 3 is mounted. Here, the thickness of the circuit layer 12 (aluminum plate 22) is set within a range of 0.1 mm or more and 1.0 mm or less, and is set to 0.6 mm in the present embodiment.

  As shown in FIG. 5, the metal layer 13 is formed by joining an aluminum plate 23 made of aluminum or an aluminum alloy to the other surface of the ceramic substrate 11. In the present embodiment, a 4N aluminum rolled plate having a purity of 99.99 mass% or more is used as the aluminum plate 23 constituting the metal layer 13. Here, the thickness of the metal layer 13 (aluminum plate 23) is set within a range of 0.1 mm to 6.0 mm, and is set to 2.0 mm in the present embodiment.

And in the power module substrate 30 with a heat sink which is this embodiment, the heat sink 31 and the metal layer 13 are joined by solid phase diffusion joining via the joining material 50 (refer FIG. 5) which consists of copper or a copper alloy. ing.
Here, as shown in FIGS. 2 and 3, the Cu atoms of the bonding material 50 and the Al atoms of the heat sink 31 and the metal layer 13 are solid-phase diffused at the bonding interface between the heat sink 31 and the metal layer 13. A diffusion bonding layer 40 having an intermetallic compound of Al and Cu is formed. In the present embodiment, the thickness t ₀ of the diffusion bonding layer 40 is in the range of 3 μm to 110 μm.

As shown in FIG. 3, the diffusion bonding layer 40 is configured so that intermetallic compounds having a plurality of compositions are stacked in accordance with the abundance ratio of Al atoms and Cu atoms. In this embodiment, a phase having a high abundance ratio of Al atoms such as the θ phase is formed on the metal layer 13 side and the heat sink 31 side, and a phase having a high Cu atom abundance ratio is present in the center of the thickness of the diffusion bonding layer 40. Is formed.
In the present embodiment, the thickness t ₁ of the high concentration Cu layer 42 at which the Cu concentration is 50 mol% or more is set to 30 μm or less.

  Next, a method for manufacturing the power module substrate with heat sink 30 according to the present embodiment described above will be described with reference to FIGS.

(Aluminum plate joining step S01)
First. As shown in FIG. 5, the aluminum plate 22 to be the circuit layer 12 and the aluminum plate 23 to be the metal layer 13 are bonded to the ceramic substrate 11. In this embodiment, the aluminum plate 22 made of a 2N aluminum rolled plate, the aluminum plate 23 made of a 4N aluminum rolled plate, and the ceramic substrate 11 made of AlN are joined together by an Al—Si brazing material 24.

In this aluminum plate joining step S01, first, an aluminum plate 22 and an aluminum plate 23 are laminated on one surface and the other surface of the ceramic substrate 11 via an Al—Si brazing material 24, respectively (aluminum plate lamination step). S11).
Next, the laminated ceramic substrate 11, the aluminum plate 22, and the aluminum plate 23 are loaded in a heating furnace in a vacuum or argon atmosphere with a load of 0.1 MPa or more and 3.5 MPa or less loaded in the lamination direction, By maintaining the temperature at 600 ° C. or higher and 650 ° C. or lower and 0.5 hour or longer and 3 hours or shorter, a molten metal region is formed between the ceramic substrate 11 and the aluminum plate 22 or aluminum plate 23 (heating step S12).
Thereafter, the molten metal region is solidified by cooling (solidification step S13). In this way, the aluminum plate 22, the ceramic substrate 11, and the aluminum plate 23 are joined to form the circuit layer 12 and the metal layer 13. Thereby, the board | substrate 10 for power modules in this embodiment is manufactured.

(Heat sink joining step S02)
Next, the heat sink 31 is bonded to the other surface of the metal layer 13 of the power module substrate 10 (the surface opposite to the bonding surface with the ceramic substrate 11).
In this heat sink bonding step S02, first, as shown in FIG. 5, a bonding material 50 made of copper or a copper alloy and a heat sink 31 are sequentially laminated on the other surface side of the power module substrate 10 (heat sink). Lamination process S21).
Here, the thickness of the bonding material 50 is set to 1 μm or more and less than 50 μm. In the present embodiment, a copper foil (thickness 10 μm) made of oxygen-free copper is used as the bonding material 50.

Then, the power module substrate 10, the bonding material 50, and the heat sink 31 are placed in a vacuum heating furnace in a state where a load of 0.29 MPa to 3.5 MPa is applied in the stacking direction. Then, solid phase diffusion bonding is performed by holding at a temperature of 400 ° C. or higher and lower than 548 ° C. for 0.1 hour or more and 4 hours or less (solid phase diffusion bonding step S22). A desirable temperature range at the time of solid phase diffusion bonding is a range from 548 ° C. (not including the eutectic temperature) which is a eutectic temperature of Al and Cu to a eutectic temperature of −5 ° C.
In the present embodiment, the respective surfaces to be bonded between the metal layer 13 and the bonding material 50 and the heat sink 31 and the bonding material 50 are solid-phase diffusion after scratches on the surfaces have been removed and smoothed in advance. It is joined.
In this way, the power module substrate with heat sink 30 according to the present embodiment is manufactured.

(Semiconductor element bonding step S03)
Next, the semiconductor element 3 is joined to one surface of the circuit layer 12 of the power module substrate 10 by soldering.
Through the above steps, the power module 1 shown in FIG. 2 is produced.

According to the power module substrate 30 with a heat sink according to the present embodiment configured as described above, the metal layer 13 composed of aluminum or an aluminum alloy (2N aluminum and 4N aluminum in the present embodiment), the heat sink 31, Are bonded by solid phase diffusion bonding via a bonding material 50 made of copper or a copper alloy (oxygen-free copper in this embodiment), and Al and Cu are bonded to the bonding interface between the metal layer 13 and the heat sink 31. A diffusion bonding layer 40 having an intermetallic compound is formed, and in this diffusion bonding layer 40, the thickness t ₁ of the high concentration Cu layer 42 having a Cu concentration of 50 mol% or more is set to 30 μm or less. Therefore, at the bonding interface between the metal layer 13 and the heat sink 31, the region where the abundance ratio of Cu atoms is high is thin, and the θ phase is a relatively brittle phase. So as to be in contact, intermetallic phases such as eta ₂ phase is a high hardness phase (CuAl) and zeta _2-phase (Cu 55 _{Al 45)} is not formed thick, even when severe heat cycle is loaded The formation of cracks in the intermetallic compound phase can be suppressed.
In order to reliably suppress the formation of cracks at the bonding interface between the metal layer 13 and the heat sink 31 when a heat cycle is applied, the Cu concentration in the diffusion bonding layer 40 is a high concentration of 50 mol% or more. The thickness t ₁ of the concentration Cu layer 42 is preferably 15 μm or less, and more preferably 5 μm or less.

Furthermore, in this embodiment, the thickness t ₀ of the diffusion bonding layer 40 having an intermetallic compound of Al and Cu formed between the metal layer 13 and the heat sink 31 is 3 μm or more. The layer 13 and the heat sink 31 are securely bonded, and the bonding strength can be ensured.
On the other hand, since the thickness t ₀ of the diffusion bonding layer 40 is less 110 [mu] m, even when severe heat cycle is loaded, it is possible to suppress the generation of cracks in the diffusion bonding layer 40.

  From the above, according to the power module substrate 30 with a heat sink according to the present embodiment, even when a severe heat cycle is applied, an intermetallic compound phase is formed at the bonding interface between the metal layer 13 and the heat sink 31. In addition, it is possible to suppress the occurrence of cracks and the like in the diffusion bonding layer and to obtain excellent bonding reliability.

  Moreover, since the power module 1 according to the present embodiment includes the power module substrate 30 with the heat sink described above, the power module substrate 10, the heat sink 31, and the heat module 31 even when a severe heat cycle is applied. It is possible to suppress a decrease in the bonding rate between the two, and an increase in thermal resistance is suppressed. For this reason, the heat generated from the semiconductor element 3 can be efficiently dissipated to the heat sink 31 side.

Furthermore, according to the method for manufacturing a power module substrate with a heat sink according to the present embodiment, in the heat sink joining step S02 for joining the metal layer 13 and the heat sink 31, copper or copper is interposed between the metal layer 13 and the heat sink 31. Solid-phase diffusion bonding is performed through a bonding material 50 made of an alloy (oxygen-free copper in the present embodiment). Since the thickness of the bonding material 50 is less than 50 μm, solid-phase diffusion bonding is performed. At this time, by sufficiently diffusing Cu atoms in the bonding material 50 to the metal layer 13 side and the heat sink 31 side, a region having a high Cu atom existing ratio is not formed thickly at the bonding interface between the metal layer 13 and the heat sink 31. , prevent the high concentration Cu layer 42 Cu concentration such as eta ₂ phase (CuAl) and zeta _{2-phase (Cu} 55 _{Al 45)} is equal to or greater than 50 mol% is formed thickly Kill.
On the other hand, since the thickness of the bonding material 50 made of copper or a copper alloy (oxygen-free copper in this embodiment) is 1 μm or more, Cu that is solid phase diffused with Al atoms of the metal layer 13 and Al atoms of the heat sink 31. Atoms can be secured and the metal layer 13 and the heat sink 31 can be reliably bonded by solid phase diffusion bonding.

In order to further reduce the thickness of the high-concentration Cu layer 42 having a Cu concentration of 50 mol% or more, the upper limit of the thickness of the bonding material 50 is preferably 30 μm or less, and more preferably 15 μm or less. preferable.
Further, in order to reliably bond the metal layer 13 and the heat sink 31 by solid phase diffusion bonding and further improve their bonding strength, the lower limit of the thickness of the bonding material 50 is preferably 5 μm or more, More preferably, it is 10 μm or more.

In the present embodiment, in the heat sink joining step S02, the metal layer 13 and the heat sink 31 are laminated through the joining material 50, and a load of 0.29 MPa to 3.5 MPa is applied in the lamination direction. Since the metal layer 13 and the heat sink 31 are solid-phase diffusion bonded by holding at a holding temperature of 0.1 ° C. or more and less than 548 ° C. for 0.1 hour or more and 4 hours or less, the metal layer 13 and the heat sink 31 are In addition to being able to bond reliably, Cu atoms of the bonding material 50 can be sufficiently diffused, and at the bonding interface between the metal layer 13 and the heat sink 31, a η ₂ phase (CuAl) or a ζ ₂ phase (Cu ₅₅ Al ₄₅ ) and the like, and the high concentration Cu layer 42 in which the Cu concentration is 50 mol% or more can be reliably suppressed.

As mentioned above, although embodiment of this invention was described, this invention is not limited to this, It can change suitably in the range which does not deviate from the technical idea of the invention.
For example, although the aluminum plate which comprises a circuit layer and a metal layer was demonstrated as what was comprised with 2N aluminum whose purity is 99 mass% or more and 4N aluminum whose purity is 99.99 mass% or more, it is limited to this. Alternatively, it may be composed of other pure aluminum or aluminum alloy.
In the present embodiment, the heat sink has been described as being composed of A6063. However, the heat sink is not limited to this and may be composed of other pure aluminum or aluminum alloy.

  In the present embodiment, the entire metal layer has been described as being made of aluminum or an aluminum alloy. However, the present invention is not limited to this. For example, as shown in FIG. The surface should just be comprised with aluminum or aluminum alloy. In the power module substrate with heat sink 130 and the power module 101 shown in FIG. 6, the metal layer 113 has a structure in which a copper layer 113A and an aluminum layer 113B are laminated, and the ceramic substrate 11 and the copper layer 113A. The aluminum layer 113B and the heat sink 131 are bonded via a bonding material, and the diffusion bonding layer 40 is formed at the bonding interface between the aluminum layer 113B (metal layer 113) and the heat sink 131. In FIG. 6, the circuit layer 112 also has a structure in which a copper layer 112 </ b> A and an aluminum layer 112 </ b> B are laminated, and the semiconductor element 3 is joined to the aluminum layer 112 </ b> B via the solder layer 2.

  Similarly, in this embodiment, the entire heat sink has been described as being made of aluminum or an aluminum alloy. However, the present invention is not limited to this. For example, as shown in FIG. The surface should just be comprised with aluminum or aluminum alloy. In the power module substrate 230 with a heat sink and the power module 201 shown in FIG. 7, the heat sink 231 has a structure in which an aluminum layer 231B made of aluminum or aluminum alloy and a heat sink body 231A made of copper or copper alloy are laminated. The metal layer 213 and the aluminum layer 231B are bonded via a bonding material, and the diffusion bonding layer 40 is formed at the bonding interface between the metal layer 213 and the aluminum layer 231B (heat sink 231).

  In the present embodiment, the circuit layer is described as being made of aluminum or an aluminum alloy. However, in the present invention, the structure of the circuit layer is not limited, and the design can be changed as appropriate. For example, the circuit layer 112 may be made of copper or a copper alloy, and the circuit layer 112 may have a laminated structure of a copper layer 112A and an aluminum layer 112B, as in the power module substrate 130 with heat sink and the power module 101 shown in FIG. May be.

Further, in the present embodiment, the bonding material has been described as being made of oxygen-free copper, but is not limited to this, and may be made of other copper or copper alloy.
In the present embodiment, the copper foil is used as the bonding material. However, the present invention is not limited to this, and the bonding material is interposed between the metal layer and the heat sink by plating, vapor deposition, sputtering, or the like. It may be interposed.

  Furthermore, in this embodiment, although the aluminum plate used as a circuit layer and a metal layer, and the ceramic substrate were demonstrated as what joins using an Al-Si type | system | group brazing material, it is not limited to this, Transient You may join using a liquid phase bonding method (Transient Liquid Phase Bonding), a casting method, a metal paste method, etc.

In the present embodiment, the insulating layer is described as being composed of a ceramic substrate made of AlN. However, the present invention is not limited to this, and other ceramic substrates such as Si ₃ N ₄ and Al ₂ O ₃ are used. It may be used.
Furthermore, the thicknesses of the insulating layer, the circuit layer, the metal layer, and the heat sink are not limited to the present embodiment, and the design may be changed as appropriate.

A confirmation experiment conducted to confirm the effectiveness of the present invention will be described.
According to the procedure described in the flow chart of FIG. 5, solid phase diffusion bonding is performed in a vacuum heating furnace (10 ⁻⁶ Pa or more and 10 ⁻³ Pa or less) under the conditions of a load of 1.2 MPa, a temperature of 535 ° C., and 1.5 hours. Then, a power module substrate with a heat sink was produced.
The ceramic substrate was made of AlN, and had a size of 40 mm × 40 mm and a thickness of 0.635 mm.

The circuit layer was formed by bonding a 4N aluminum rolled plate (37 mm × 37 mm, thickness 0.6 mm) having a purity of 99.99 mass% or more to a ceramic substrate using an Al—Si brazing material.
The metal layer was formed by joining a 4N aluminum rolled plate (37 mm × 37 mm, thickness 0.6 mm) having a purity of 99.99 mass% or more to a ceramic substrate using an Al—Si brazing material.
The heat sink was made of the materials shown in Table 1, and was 50 mm × 50 mm and 5 mm thick.
Here, the bonding material having the composition and thickness shown in Table 1 was used. A material having a thickness of 5 μm or more was used as a foil material, and a material having a thickness of less than 5 μm was formed by plating.

Further, as a conventional example, the following power module substrate with a heat sink was produced.
A 2N aluminum rolled plate (37 mm × 37 mm, thickness 0.6 mm) to be a circuit layer, a ceramic substrate (40 mm × 40 mm, thickness 0.635 mm) made of AlN, and a 4N aluminum rolled plate to be a metal layer ( 37 mm × 37 mm, thickness 0.6 mm) and was laminated with an Al-Si based brazing material, in a state pressurized at 5 kgf / cm ² in the stacking direction, and charged in a vacuum heating furnace, 650 ° C. Were joined by heating for 30 minutes to produce a power module substrate. Next, the power module substrate and a Ni-plated heat sink (A6063 rolled plate, 50 mm × 50 mm, thickness 5 mm) were joined via Sn—Ag—Cu solder.

(Cross-section observation of specimen)
Using a cross section polisher (SM-09010 made by JEOL Ltd.), the cross section of the obtained power module substrate with heat sink is ion acceleration voltage: 5 kV, processing time: 14 hours, protrusion amount from shielding plate: 100 μm Observed after ion etching, the thickness t ₀ of the diffusion bonding layer formed at the bonding interface between the metal layer and the heat sink, and the thickness t ₁ of the high concentration Cu layer at which the Cu concentration is 50 mol% or more were measured. .
Thickness t ₀ of the diffusion bonding layer is EPMA (JXA-8530F manufactured by JEOL Ltd., acceleration voltage: 15 kV, spot diameter: 1 μm or less, magnification: 500 times, interval in the thickness direction at the bonding interface between the metal layer and the heat sink. : 0.3 μm), a line analysis was performed, and the portion where the Cu concentration was 1 at% or more was regarded as a diffusion bonding layer, and the thickness was measured.
The thickness t ₁ of the high-concentration Cu layer at which the Cu concentration is 50 mol% or more is such that the junction interface between the metal layer and the heat sink is EPMA (JXA-8530F, manufactured by JEOL Ltd., acceleration voltage: 15 kV, spot) A line analysis is performed at a diameter of 1 μm or less, a magnification of 500 times, and an interval of 0.3 μm), and a portion where Al / Cu (atomic ratio) is 1 or more is a high concentration Cu layer having a Cu concentration of 50 mol% or more. The thickness was measured.

(Heat cycle test)
In the heat cycle test, TSB-51 manufactured by Espec Corp. is used, and the test piece (power module with heat sink) is in the liquid phase (−40 ° C. × 5 minutes ← → 150 ° C. × 5). A minute heat cycle was performed 4000 times.
And the joining rate before a heat cycle test and the joining rate after a heat cycle test were evaluated.

(Joining rate)
The joining rate between the metal layer and the heat sink was determined using the following formula using an ultrasonic flaw detector (FineSAT 200 manufactured by Hitachi Power Solutions). Here, the initial bonding area was an area (37 mm square) to be bonded before bonding. In the image obtained by binarizing the ultrasonic flaw detection image, the peeling is indicated by the white portion in the joint portion. Therefore, the area of the white portion is defined as the peeling area.
(Bonding rate) = {(initial bonding area) − (peeling area)} / (initial bonding area)

  The evaluation results are shown in Table 1.

In the conventional example, the joining rate greatly decreased after the heat cycle test. It is presumed that cracks occurred in the solder layer due to the heat cycle.
Also in Comparative Example in which the thickness t ₁ of the high density layer of Cu Cu concentration of more than 50 mol% is more than 30 [mu] m, the bonding ratio after the heat cycle test was greatly reduced. A hard phase including η ₂ phase (CuAl) and ζ ₂ phase (Cu ₅₅ Al ₄₅ ) is formed thick so as to be adjacent to the fragile θ phase formed on the metal layer and the heat sink side, and the θ phase is formed by heat cycle. This is presumed to be caused by cracks.

On the other hand, according to the example of the present invention in which the thickness t ₁ of the high-concentration Cu layer at which the Cu concentration is 50 mol% or more is 30 μm or less, the bonding rate is not greatly reduced after the heat cycle test. It was confirmed that the bonding reliability was excellent.
From the above, according to the present invention, it was confirmed that it is possible to provide a power module substrate with a heat sink that can suppress the occurrence of cracks and the like at the joint interface even when a severe heat cycle is applied. .

1, 101, 201 Power module 10, 110, 210 Power module substrate 11 Ceramic substrate 12, 112, 212 Circuit layer 13, 113, 213 Metal layer 30, 130, 230 Power module substrate with heat sink 31, 131, 231 Heat sink 40 Diffusion bonding layer 42 High-concentration Cu layer 50 Bonding material

Claims (3)

An insulating layer; a circuit layer formed on one surface of the insulating layer; a metal layer formed on the other surface of the insulating layer; and a surface of the metal layer opposite to the insulating layer. Heat sink, and a power module substrate with a heat sink,
The bonding surface with the heat sink among the metal layers, and the bonding surface with the metal layer among the heat sinks are made of aluminum or aluminum alloy,
The metal layer and the heat sink are bonded by solid phase diffusion bonding via a bonding material made of copper or a copper alloy,
A diffusion bonding layer having an intermetallic compound of Al and Cu is formed at the bonding interface between the metal layer and the heat sink, and in this diffusion bonding layer, a high concentration Cu having a Cu concentration of 50 mol% or more. A power module substrate with a heat sink , wherein the thickness of the layer is 30 μm or less, and the thickness of the diffusion bonding layer is in the range of 3 μm to 110 μm . 2. A power module comprising: the power module substrate with a heat sink according to claim 1; and a semiconductor element bonded to a surface of the circuit layer opposite to the insulating layer. An insulating layer; a circuit layer formed on one surface of the insulating layer; a metal layer formed on the other surface of the insulating layer; and a surface of the metal layer opposite to the insulating layer. A method of manufacturing a power module substrate with a heat sink comprising:
Of the metal layer, the bonding surface with the heat sink, and the bonding surface with the metal layer of the heat sink is made of aluminum or aluminum alloy,
A heat sink joining step for joining the metal layer and the heat sink, and in this heat sink joining step, solid phase diffusion joining is performed between the metal layer and the heat sink via a joining material made of copper or a copper alloy. It is made up of
The bonding material has a thickness in the range of 1 μm or more and less than 50 μm ,
In the heat sink bonding step, the metal layer and the heat sink are stacked via the bonding material, and the load is maintained at 400 ° C. or higher and lower than 548 ° C. with a load of 0.29 MPa or higher and 3.5 MPa or lower loaded in the stacking direction. A method for producing a substrate for a power module with a heat sink , wherein the metal layer and the heat sink are solid-phase diffusion bonded by holding at a temperature of 0.1 hours to 4 hours .

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